1. Field of the Invention
The present invention relates to a power module that converts a direct current into an alternating current, and particularly to a power module in which a semiconductor device is mounted on a substrate.
2. Description of the Related Art
A power module switches a switching device such as an insulating gate bipolar transistor (IGBT), thereby converts a direct current supplied from a direct current power supply into an alternating current, and drives an alternating-current motor or the like by the alternating current. In particular, a power module with which a control circuit for the switching device is integrated is referred to as an intelligent power module (IPM). A heating value of the IGBT or the like is large, and accordingly, in the power module, heat radiation from the device becomes a problem. Therefore, there are taken measures for cooling the power module, for example, disposition of a cooling mechanism such as a heat radiation plate that radiates heat generated by the switching device.
However, a surface of the device that composes the power module is thermally insulated by gel or the like, and accordingly, the heat generated by the device is radiated from only a back surface of the device, which is in contact with the substrate. Therefore, cooling efficiency has been low, and it has been necessary to radiate the heat by disposing a large cooling mechanism on the substrate. As a result, it has been difficult to miniaturize the power module.